Load and Generation Converters Control Strategy to Enhance the Constant Power Load Stability Margin in a DC Microgrid

Integrating Constant Power Loads (CPL) in a DC microgrid generates a virtual negative impedance that may lead to system instability. CPL deteriorates the system damping, which is more severe for the DC power system with large line impedances. This paper proposes a novel and simple virtual negative resistance-based control loop for the DC-DC converters connected at both source and load ends to enhance the CPL stability margin in a DC microgrid. The proposed control scheme includes a simple pole-zero criterion to evaluate the virtual negative resistance. Further, small-signal and extended large-signal models of the bidirectional DC-DC converters are developed to calculate stabilizer parameters and assess system stability with CPL. These models effectively calculate optimal stabilizer parameter values using simple root locus analysis. A comparative stability analysis is conducted to illustrate the system's resilience in the face of changes in parameter values and considerable enhancement of the stability margin. The eigenvalue analysis and time domain simulations are performed with the proposed control strategy at the source and load side converters without affecting the load side voltage profile to demonstrate its effectiveness.